▲ Sleep
"Even after getting enough sleep, I feel tired in the morning."
This is often not simply because of getting too little sleep, but rather because people wake up multiple times, failing to achieve deep sleep. In particular, Korean women were found to have shorter baseline sleep durations than American and European women, and the decline in their sleep quality begins at an earlier stage.
According to the latest issue of the international journal Sleep, a joint research team from Samsung Electronics and institutions in the U.S. and Canada examined approximately 3.8 million nights of sleep data recorded by Galaxy Watches from 192,500 women aged 20 to 65 across the United States, South Korea, Germany, France, and the United Kingdom.
The metric the research team focused on the most is Wake After Sleep Onset (WASO), which refers to the time spent awake after initially falling asleep and before finally waking up in the morning.
This serves as an indicator of sleep quality, showing how frequently a person wakes up throughout the night and how much they toss and turn.
The analysis showed that WASO tends to increase sharply around the menopausal transition.
By age group, compared to women aged 20 to 24, those aged 50 to 54 stayed awake longer by an average of 5.4 minutes (15.3%), those aged 55 to 59 by 8.8 minutes (24.9%), and those aged 60 to 64 by 11.2 minutes (31.7%).
In contrast, actual sleep duration decreased by only about 13 minutes in the early 50s and about 17 minutes in the early 60s.
This suggests that the biggest change for women after middle age is not sleeping less, but rather the inability to maintain continuous sleep.
For men, nighttime wakefulness also increased with age, but the magnitude of the increase was much more gradual than that of women.
In particular, women experienced the largest increase in WASO during the transition from ages 45–49 to 50–54, whereas men did not show similar changes until around age 60.
The research team noted that these differences suggest the influence of hormonal changes associated with women's menopausal and perimenopausal transitions.
What draws attention is that the sleep duration of Korean women was significantly shorter than that of Western women.
Compared to American women, Korean women had an average total sleep window—from falling asleep to waking up in the morning—that was 27.1 minutes shorter, and their actual sleep duration, excluding WASO, was 24.7 minutes shorter on average.
These differences were even greater when compared with women in Germany, France, and the UK.
Changes in sleep quality were also identified.
While nighttime wakefulness among American and European women clearly increased starting around age 50, the increase for Korean women began as early as their early 30s.
By their mid-30s, Korean women exhibited levels of nighttime wakefulness nearly identical to those of Western women, and showed similar upward trends thereafter.
The research team interprets that South Korea's long working hours culture, late bedtimes, social stress, and lifestyle habits unique to the Asian region may have influenced these differences.
Sleep experts point out that sleep problems in menopausal women should not be dismissed simply as a natural phenomenon of aging.
In fact, studies have consistently reported that menopausal sleep disorders are associated not only with fatigue and irritability, but also with decreased concentration, lower quality of life, reduced work productivity, and an increased risk of cardiovascular and metabolic diseases.
If nighttime waking symptoms persist for more than a few weeks, it is helpful to consult a medical specialist to identify the cause and practice lifestyle improvements such as maintaining regular sleep habits, exercising, and managing caffeine and alcohol intake.
The research team stated, "This result is one of the largest-scale studies objectively demonstrating sleep changes in middle-aged women, as it analyzed 3.8 million nights of sleep data accumulated in real-life settings," adding, "Wearable devices like smartwatches can objectively record sleep changes over a long period, which can help medical staff consult patients or establish personalized management strategies."
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